Human immunodeficiency virus (HIV) has been shown to be the etiologic agent for acquired immune deficiency syndrome (AIDS) (Barre-Sinoussi et al., "Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS)," Science, 220:868-871 (1983) and Gallo et al., "Frequent detection and isolation of cytopathic retroviruses (HTLV-III) from patients with AIDS or at risk for AIDS," Science, 224:500-503 (1984)). An antibody response to HIV indicates exposure and infection. Current clinical assays for antibodies to HIV are viral based enzyme immunoassays (EIA). Viral lysate EIAs offer the advantage of high sensitivity but the disadvantage of high rates of false positives, of being slow, requiring several hours to complete a test, and the further disadvantage of requiring sophisticated instrumentation that is not available in all laboratories.
A latex agglutination assay based on purified HIV-specific antigen could offer the advantages of relatively high sensitivity, specificity, speed, and simplicity in situations where the time and technology required for EIA may not be available or appropriate. Latex agglutination is a technology which, unlike EIA, is a direct assay for specific antibodies. This test is based upon cross-linking antigen attached to microbeads with antibodies to form visible aggregates. Latex microbeads are negatively charged and antigen may bind to the microbeads by means of hydrophobic and ionic adsorption rather than by covalent attachment. Because of the fatal nature of HIV infection, it is important that any latex agglutination assay developed for determining the presence of antibodies to HIV in an individual at risk be very accurate.